Technical Field
The present disclosure generally relates to a medical device used to provide localized therapeutic hypothermia at a small situs. More particularly, but not exclusively, the present disclosure relates to a device that reduces temperature in the area around a cochlea during a medical procedure to implant an auditory prostheses.
Description of the Related Art
In many medical procedures, a medical practitioner accesses internal loci of a patient. In some cases, the medical practitioner accesses the internal loci for diagnostic purposes. In other cases, the practitioner accesses the loci to provide treatment. In still other cases, different therapy is provided.
FIG. 1 illustrates the anatomy of a human ear. In FIG. 1, the cartilage and fleshy tissue of the right, outer ear 12 is shown. The external auditory canal 14 provides a pathway for sound to enter the middle ear. The external auditory canal 14 passes through the external and internal acoustic meatus of the skull, which forms a space near the floor of the skull 16 and the upper bone 18 of the mandible. The middle ear includes the tympanic membrane 20, which is more readily known as the eardrum, and the tympanic cavity 22. Sound waves pass through the ear drum and into the tympanic cavity 22. The middle ear transfers the sound waves to the fluid of the cochlea 30. To help orient the anatomical features illustrated in FIG. 1, the Eustachian tube 24, semicircular canals 26, vestibular nerve 28, and cochlear nerve 32 are also shown.
The rolled up spiral of the cochlea 30 looks like a snail shell (“cochlea” is a Greek word for snail) and functions to transform the vibrations of the cochlear liquids and associated structures into a neural signal. The neural signal is sensed by the cochlear nerve 32 and passed into the auditory structures of the brain.
Along the spiral of the cochlea 30, various frequencies are noted in FIG. 1. An area at the entrance (base) of the cochlea 30 is indicated at 16 kilohertz (kHz); a second area at 1 kHz and a third area at 0.5 kHz are also identified. Generally speaking, higher frequencies (e.g., 20 kHz to about 1.5 kHz) are sensed at the base of the cochlea 30, mid-range frequencies (e.g., 1.5 kHz to about 600 Hz) are sensed in the middle of the cochlea 30, and lower frequencies (e.g., 600 Hz to about 200 Hz) are sensed toward the tip of the cochlea 30.
FIGS. 2A-2C illustrates three cutaway portions of a cochlea 30. In FIG. 2A, a terminal end portion of the cochlea 30 is shown along with a cochlear duct 34. Long cilia 36 (i.e., hair cells) are shown. The long, flexible hair cells are formed to tune to the lower frequencies sensed at the tip of the cochlea 30. Mid-range frequencies are sensed by the medium cilia 38 shown in FIG. 2B, and high frequencies are sensed by the short cilia 40 shown in FIG. 2C.
When parts of the ear that transmit sound to the cochlear nerve 32 are damaged, the person will experience partial or total hearing loss. In the case of mild or moderate hearing loss, the person often benefits from a hearing aid, which is an amplifier worn in the external auditory canal 14. The hearing aid amplifies sound so that a more intense sound wave is passed into the middle ear. In cases where the sound reception mechanism in the cochlea 30 is more severely damaged however, the hearing aid is of little help. One alternative to a hearing aid for a select group of patients is cochlear implant.
FIG. 3 illustrates a cochlear electrode array 46 implanted in a human cochlea 30. The cochlear electrode array 46 bypasses the damaged part of the ear and transmits sound signals directly to the cochlear nerve. Signals provided at the cochlear electrode array 46 originate at a cochlear transmitter 42 and pass down a cochlear probe 44. The cochlear probe passes through a hole in the skull. When the device is operating, external sound is picked up by a microphone (not shown) worn behind the patient's ear. The sound is electronically processed and passed to a stimulator/transmitter. Sequences of electrical pulses are passed down the cochlear probe 44 to the cochlear electrode array. The electrodes of the array stimulate the cochlear nerve, thereby bypassing the damaged portions of the middle and inner ear. Each electrode in the array is tuned to a particular frequency range so as to mimic the frequency separation and identification mechanism of a healthy ear.